Invar effect and noncollinear magnetism in FeCu alloys

This is the authors' abstract. We don't add key points for this paper.

The Invar effect has been observed in many Fe rich alloys, most famously Ni Invar. Generally the Invar behavior is associated with the strong coupling between the lattice and magnetic degrees of freedom, and therefore depends on the magnetic ordering in these alloys. Recent experimental works observed an Invar effect in fcc-FeCu solid solutions [Gorria et al., Phys. Rev. B 69, 214421 (2004)]. In the present paper the magnetic states of fcc-FeCu solid solutions for various concentrations are investigated. The first principles calculations employ the locally self-consistent multiple scattering real space method for solving the local-density approximation Kohn–Sham equation to investigate the noncollinear ordering of magnetic moments. The magnetic order for the low iron concentration is found to be noncollinear, spin glasslike, and the ferromagnetic order is not stable, whereas for the iron rich alloys for the ground state equilibrium lattice constants a magnetic order with parallel aligned Fe moments is stable. In this configuration the induced moments at the Cu sites order nontrivially on a cone with an opening of approximately 40° around the Fe moment direction.